DOMINION used to load some kind of PINK smokeless in their rounds, back before they were discontinued in 1968.
Correct loading for the .43 Mauser (allright, purists, 11.15x60R Model 1871) is a .446" diameter round-nosed lead slug weighing 386 grains, propelled by 77 grains of Black powder.
You can substitute SR-4759 for the Black in a 38%-of-Black formula and get the same velocities with the same pressures. For the .43, this would be 77(your Black charge)x.38= 29.26 grains of SR-4759. The SR-4759 was regarded for many years as the perfect replacement for Black in cartridge rifles and was listed as such in many of the older manuals. I have a friend who was shooting it in his .300 Weatherby, bringing it down to under .30-30 power levels, just for fun. It has gone out of production.... and been brought back again because it is needed..... more times than I can remember in my 50 years of shooting.
You can get a nice set of dies from LEE PRECISION (your local gun shop can order them in for you). These come WITH the very special shellholder for this cartridge, so no troubles there. Bruno Gross up in Fairview, Alberta, definitely has brass; I think he calls himself Grizzly Shooting Supply, but he's in the phone book. I don't know of any moulds for bullets in Canada, but there were a couple of nice ones listed last time I got onto MIDWAY's website, starting about 62 US clams..... which is $62.31 by yesterday's rate, so not a horrid penalty for being Canadian this time. And it's only a TOOL, so there shouldn't be any insane surcharge for shipping..... at least, one would HOPE.
Good luck with the little Mouser. They can be a lot of fun!